1. Field of the Invention
The present invention relates to a switch, and in particular to a call cut-off detection circuit for a switch and a method of the same which are capable of implementing a good quality call and enhancing a reliability of the switch by detecting a call cut-off based on a simple method.
2. Description of the Conventional Art
Generally, a call cut-off occurs during a call. The call cut-off case is classified into a case that a call is inputted from a telephone terminal and is allocated to an audio channel(PCM channel) at a base station and uses a trunk of a switch, and then is cut off, and a case that a call is cut off due to an external environment before a stop button of the telephone terminal is pushed. The above-described two cases are called a call cut-off.
FIG. 1 illustrates a conventional electric circuit which includes a processor 10, a time switch unit 20, a local link unit 30, a central link unit 40, and a space switch 50.
The processor 10 controls a call process and a maintenance of a switch and controls the time switch 20. The local link unit 30 outputs a 8-bit PCM data outputted from the time switch 20 to the central link unit 40 through a STM-1 framer, and the 8-bit PCM data inputted from the central link unit 40 is outputted to the time switch 20. In addition, the space switch 50 switches the 8-bit PCM data inputted from the central link unit 40 by the highway, and outputs the 8-bit PCM data inputted from another subscriber or another switch to the central link unit 40.
The time switch 20 includes a speech memory storing the 8-bit PCM data as a block for receiving the 8-bit PCM data from the subscriber and performing an interchange of the time slot, and a write address generator 12 and a read address generator 13 for generating a write and read address WA and RA to the speech memory 11 in accordance with a clock signal CP2 of 16.384 MKHz and a frame pulse signal FP2 of 8 KHz.
The operation of the conventional electric switch will be explained with reference to FIG. 1.
The 8-bit PCM data inputted to an externally connected subscriber terminal is stored into the speech memory 11 by the channel in accordance with the write address WA outputted from the write address generator 12, and the thusly stored 8-bit PCM data is outputted to the local link unit 30 in accordance with a read address RA outputted from the read address generator 13. At this time, the read address generator 13 is controlled by the processor 10. Therefore, the local link unit 30 outputs the 8-bit PCM data outputted from the speech memory 11 to the central link unit 40 and the space switch 50 through a high speed link of 155.520 Mbps.
When the 8-bit PCM data switched by the space switch 50 is inputted through the central link unit 40 and the local link unit 30, the 8-bit PCM data is stored into the speech memory 11 by the channel in accordance with the write address WA outputted from the write address generator 12. Therefore, the 8-bit PCM data stored in the speech memory 11 is outputted to the telephone terminal in accordance with the rear address RA outputted from the read address generator 13.
However, in the conventional switch, if a call cut-off occurs, a switch operator is capable of detecting a call cut-off state only based on a report from a subscriber. Namely, there is not way to detect the call cut-off state in the conventional art. Therefore, the switch operator is not capable of quickly repairing the cut-off call, so that it is impossible to increase a reliability of the switch.
Accordingly, it is an object of the present invention to provide a call cut-off detection circuit for a switch and a method of the same which overcome the aforementioned problems encountered in the conventional art.
It is another object of the present invention to provide a call cut-off detection circuit for a switch and a method of the same which are capable of quickly detecting a call cut-off occurring during a call.
It is another object of the present invention to provide a call cut-off detection circuit for a switch and a method of the same which are capable of implementing a good quality call and enhancing a reliability of the switch by detecting a call cut-off based on a simple method.
To achieve the above objects, there is provided a call cut-off detection circuit for a switch which includes a time switch unit switching a first PCM data, a COB(Cut-Off Call Bit) processing circuit combining the first PCM data and a first call state data or separating the first PCM data and a second call state data from a second PCM data, a processor writing the first call state data into the COB processing circuit and judging the state of a call cut-off of a channel based on the second call state data separated by the COB processing circuit, and a local link unit connected between the COB processing circuit and a space switch for transmitting and receiving the second PCM data.
To achieve the above objects,.there is provided a call cut-off detection method for a switch which includes the steps of storing a first call state data into a COB processing circuit, combining a first PCM data inputted from the side of a telephone terminal and the first call state data and transmitting a second PCM data to the side of a space switch, checking whether the second PCM data is inputted from the side of the space switch, separating the second PCM data inputted from the side of the space switch into a first PCM data and a second call state data, and comparing the thusly separated second call state data and first call state data and judging whether a call cut-off of a corresponding channel occurred.
Additional advantages, objects and features of the invention will become more apparent from the description which follows.